The incidence of J.O.D. less than 16 years of age will be determined for the first time in a defined community. The incidence will be related to age, sex, race and geographic area of residence. Seasonal and temporal trends will be evaluated. Secondary cases of J.O.D. within families during a 10 year follow up will be identified. The interrelationship of the demographic characteristics with HLA type, immunoglobulin and autoantibodies within and between families will be measured. Genetic analysis will include analysis of both immediate and extended families and will include HLA typing, immunoglobulin and autoantibody studies. The distribution of glucose tolerance within the families in relation to immunology, genetic and epidemiological characteristics will be considered. Viral antibody studies at the time of the initial diagnosis of a case within a family and prior to secondary case will be also be included. These studies should help determine the interrelationship of host and environmental factors in the etiology of J.O.D.